CN115394559B - Method for reducing ESR (equivalent series resistance) of graphite silver paste process of solid electrolyte sheet type tantalum capacitor - Google Patents
Method for reducing ESR (equivalent series resistance) of graphite silver paste process of solid electrolyte sheet type tantalum capacitor Download PDFInfo
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- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 title claims abstract description 141
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 133
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 133
- 239000010439 graphite Substances 0.000 title claims abstract description 133
- 229910052715 tantalum Inorganic materials 0.000 title claims abstract description 129
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims abstract description 90
- 229910052709 silver Inorganic materials 0.000 title claims abstract description 90
- 239000004332 silver Substances 0.000 title claims abstract description 90
- 238000000034 method Methods 0.000 title claims abstract description 51
- 239000003990 capacitor Substances 0.000 title claims abstract description 41
- 239000007784 solid electrolyte Substances 0.000 title claims abstract description 27
- 230000001603 reducing effect Effects 0.000 title claims abstract description 24
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims abstract description 65
- 238000001816 cooling Methods 0.000 claims abstract description 31
- 239000011259 mixed solution Substances 0.000 claims abstract description 22
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000000243 solution Substances 0.000 claims description 37
- 239000007787 solid Substances 0.000 claims description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 238000002156 mixing Methods 0.000 claims description 14
- 238000000354 decomposition reaction Methods 0.000 claims description 7
- 230000018044 dehydration Effects 0.000 claims description 4
- 238000006297 dehydration reaction Methods 0.000 claims description 4
- 239000008367 deionised water Substances 0.000 claims description 4
- 229910021641 deionized water Inorganic materials 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 238000007598 dipping method Methods 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000011265 semifinished product Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- ROSDCCJGGBNDNL-UHFFFAOYSA-N [Ta].[Pb] Chemical compound [Ta].[Pb] ROSDCCJGGBNDNL-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
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- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 239000002775 capsule Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
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- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/022—Electrolytes; Absorbents
- H01G9/025—Solid electrolytes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/04—Electrodes or formation of dielectric layers thereon
- H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
- H01G9/0425—Electrodes or formation of dielectric layers thereon characterised by the material specially adapted for cathode
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/04—Electrodes or formation of dielectric layers thereon
- H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/15—Solid electrolytic capacitors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/04—Electrodes or formation of dielectric layers thereon
- H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
- H01G2009/05—Electrodes or formation of dielectric layers thereon characterised by their structure consisting of tantalum, niobium, or sintered material; Combinations of such electrodes with solid semiconductive electrolytes, e.g. manganese dioxide
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention belongs to the technical field of capacitor manufacturing, and particularly relates to a method for reducing ESR (equivalent series resistance) of a graphite silver paste process of a solid electrolyte sheet type tantalum capacitor, which comprises the steps of preparing a graphite silver paste layer on the surface with a dielectric oxide film and a manganese dioxide layer, wherein the graphite silver paste layer is prepared by the following steps: immersing tantalum blocks in a mixed solution of aqueous graphite and manganese nitrate, and then dehydrating, decomposing and cooling to obtain a first layer of cathode; immersing the tantalum block in aqueous graphite, and then dehydrating, solidifying and cooling to obtain a second-layer cathode; immersing the tantalum block in oily graphite, and then dehydrating, solidifying and cooling to obtain a third-layer cathode; immersing the tantalum block in a mixed solution of oily graphite and silver paste, and then dehydrating, solidifying and cooling to obtain a fourth-layer cathode; immersing the tantalum block in silver paste, and then dehydrating, solidifying and cooling to obtain a fifth-layer cathode; the method reduces ESR of the solid electrolyte tantalum capacitor and improves the bonding strength of the cathode layer.
Description
Technical Field
The invention belongs to the technical field of tantalum capacitor manufacturing, and particularly relates to a method for reducing ESR (equivalent series resistance) of a graphite silver paste process of a solid electrolyte sheet type tantalum capacitor.
Background
The solid electrolyte sheet type tantalum electrolytic capacitor is one of extremely important basic electronic elements in electronic engineering, and is widely applied to various fields of communication equipment, audio-visual systems, electrical appliances and meters and the like. The ESR value of a solid electrolyte sheet tantalum electrolytic capacitor is the final value of the contact resistance of each capacitive component characterizing the internal structure of the capacitor. The tantalum block is formed by bonding and molding tantalum powder and then sintering the tantalum powder at a high temperature in vacuum, and the internal structure of the tantalum block is composed of a plurality of pore-shaped pellets, so that the contact area between tantalum powder particles is increased. The conventional cathode material is coated on a medium Ta 2 O 5 MnO of surface 2 Deposited MnO 2 The disc is faced in tunnels of pore-like structure.
The anode is usually led out from the center of the tantalum block by a metal tantalum lead wire, and the cathode is led out by coating graphite and silver paste on the cathode. Graphite can be used for improving silver paste and MnO 2 Is provided for the electrical contact of the substrate. I.e. MnO 2 The surface roughness of (2) is very porous, and since the silver paste contains an organic binder, the contact resistance is increased and the loss characteristics of the capacitor are deteriorated when the silver paste is directly coated on the surface of manganese dioxide. The dipping silver paste can reduce the contact resistance of the cathode lead-out layer, improve the conductivity of the surface of the tantalum core and improve the cathode lead-out.
ESR (Equivalent Series Resistance) is an equivalent series resistance, and the ideal capacitor does not have any energy loss, but in practice, the capacitor is made of a material having a resistance, and the insulating medium of the capacitor has a loss, and the loss is externally represented as a resistance connected in series with the capacitor, so the equivalent series resistance is called. Esr=rf+ro+rtst, where Rf is Ta, according to the decomposition of the capacitor constituent material 2 O 5 Resistance of film, film and MnO 2 The contact resistance, ro, is the MnO in the core 2 Rtst is the core appearance MnO 2 And the resistances of graphite, silver paste, and the like, and the resistances between each other.
With the rapid development of electronic technology, tantalum electrolytic capacitors are rapidly developed towards miniaturization, high reliability and long service life, and ESR is one of important parameters for representing the electrical performance of the tantalum capacitors, and the lower the ESR is, the smaller the loss is, the larger the output current is, and the higher the quality of the capacitors is.
Disclosure of Invention
The invention provides a method for reducing the ESR of a graphite silver paste process of a solid electrolyte sheet type tantalum capacitor aiming at the defects of the prior art.
The method is realized by the following technical scheme:
a method for reducing ESR of a graphite silver paste process of a solid electrolyte sheet type tantalum capacitor is to prepare a graphite silver paste layer on the surface of a tantalum core with a dielectric oxide film and a manganese dioxide layer, wherein the graphite silver paste layer is prepared by the following steps:
1) Immersing tantalum blocks in a mixed solution of an aqueous graphite solution and a manganese nitrate solution, and then dehydrating, decomposing and cooling to obtain a first layer of cathode;
2) Immersing the tantalum block in a water-based graphite solution, and then dehydrating, solidifying and cooling to obtain a second-layer cathode;
3) Immersing the tantalum block in an oily graphite solution, and then dehydrating, solidifying and cooling to obtain a third-layer cathode;
4) Immersing tantalum blocks in a mixed solution of an oily graphite solution and silver paste, and then dehydrating, solidifying and cooling to obtain a fourth-layer cathode;
5) Immersing the tantalum block in silver paste, dehydrating, solidifying and cooling to obtain the fifth-layer cathode.
The concentration of the manganese nitrate solution is 0.75-2.05 g/cm 3 。
The aqueous graphite solution is prepared by mixing aqueous graphite with deionized water, and the solid content after mixing is 0.5-15 wt%.
In the step 1), the volume ratio of the aqueous graphite solution to the manganese nitrate solution in the mixed solution is (1-8): 1.
The oily graphite solution is prepared by mixing oily graphite with deionized water, and the solid content after mixing is 15-30wt%.
The solid content of the silver paste is 25-50wt%.
In the step 4), the volume ratio of the oily graphite solution to the silver paste in the mixed solution is (2-4): 1.
The dehydration time is 5-85 min, and the dehydration temperature is 10-100 ℃.
The decomposition time is 5-20 min, and the decomposition temperature is 150-300 ℃.
The curing time is 5-60 min, and the curing temperature is 120-350 ℃.
The cooling time is 5-30 min.
The beneficial effects are that:
the method has the advantages of good lap joint of the manganese dioxide layer and the graphite layer and good lap joint of the graphite layer and the silver paste layer and small interface contact resistance, thereby reducing the ESR of the solid electrolyte tantalum capacitor, completing the manufacture of the cathode with low ESR, improving the bonding strength of the cathode layer and effectively improving the high-frequency electrical performance of the solid electrolyte tantalum capacitor.
According to the invention, the characteristics of the size, morphology, distribution and the like of particles on the surface of each cathode layer are considered, and the thought of physical matching, fitting and fixing of the particle sizes is utilized, and firstly, a manganese dioxide and water-based graphite mixed layer is utilized to realize good fit with a manganese dioxide layer and a water-based graphite layer; and then an oily graphite layer is formed on the water-based graphite layer, so that the binding force between manganese dioxide and graphite can be enhanced, and the oily graphite, the graphite layer and the silver paste layer are formed on the basis of the oily graphite layer, so that the silver paste layer and the graphite layer form good contact, and further the contact resistance is reduced.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention; 1-a manganese dioxide layer; a mixed layer of 2-manganese dioxide and aqueous graphite (first layer cathode); 3-aqueous graphite layer (second layer cathode); 4-oily graphite layer (third layer cathode); a 5-oily graphite and silver paste mixed layer (fourth layer cathode); 6-silver paste layer (fifth layer cathode);
fig. 2: SEM image of the surface morphology of the manganese dioxide/water-based graphite mixed layer in example 1.
Detailed Description
The following detailed description of the invention is provided in further detail, but the invention is not limited to these embodiments, any modifications or substitutions in the basic spirit of the present examples, which still fall within the scope of the invention as claimed. The specific conditions are not noted in the examples, and the reagents or instruments used are conventional products commercially available, which are not noted by the manufacturer, or are recommended by the manufacturer.
Example 1
A method for reducing ESR of a solid electrolyte tantalum capacitor graphite silver paste procedure is to prepare a graphite silver paste layer on the surface of a tantalum core with a dielectric oxide film and a manganese dioxide layer, wherein the graphite silver paste layer is prepared by the following steps:
1) Immersing the tantalum block in the mixed solution A, immediately taking out the tantalum block, dehydrating the tantalum block for 30min at 20 ℃, then placing the tantalum block in a film coating furnace with the temperature of 250 ℃ and the oxygen content of 5% for decomposition for 7min, and finally cooling the tantalum block at room temperature for 5min to obtain a first layer of cathode (namely a manganese dioxide and water-based graphite mixed layer); the mixed solution A is prepared from aqueous graphite solution with solid content of 0.5wt% and concentration of 0.75g/cm 3 Is prepared by mixing manganese nitrate solution according to the volume ratio of 8:1;
2) Immersing the tantalum block treated in the step 1) in an aqueous graphite solution with the solid content of 0.5wt%, immediately taking out the tantalum block, dehydrating the tantalum block for 30min at 20 ℃, solidifying the tantalum block for 30min at 180 ℃, and finally cooling the tantalum block for 5min at room temperature to obtain a second-layer cathode (namely an aqueous graphite layer);
3) Immersing the tantalum block treated in the step 2) into oily graphite with the solid content of 15wt%, immediately taking out the tantalum block, dehydrating the tantalum block for 30min at 20 ℃, solidifying the tantalum block for 30min at 180 ℃, and finally cooling the tantalum block for 5min at room temperature to obtain a third-layer cathode (namely an oily graphite layer);
4) Immersing the tantalum block treated in the step 3) in the mixed solution B, immediately taking out the tantalum block, dehydrating the tantalum block at 20 ℃ for 30min, solidifying the tantalum block at 180 ℃ for 30min, then heating to 210 ℃ for 30min, and finally cooling the tantalum block at room temperature for 5min to obtain a fourth layer of cathode (namely an oily graphite and silver paste mixed layer); the mixed solution A is formed by mixing an oily graphite solution with the solid content of 15wt% and silver paste with the solid content of 25wt% according to the volume ratio of 3:1;
5) Immersing the tantalum block treated in the step 4) into silver paste with the solid content of 25wt%, immediately taking out the tantalum block, dehydrating the tantalum block for 30min at 20 ℃, solidifying the tantalum block for 30min at 210 ℃, and finally cooling the tantalum block for 5min at room temperature to obtain a fifth-layer cathode (namely a silver paste layer);
comparative example 1
A method for reducing ESR of a solid electrolyte tantalum capacitor graphite silver paste procedure is to prepare a graphite silver paste layer on the surface of a tantalum core with a dielectric oxide film and a manganese dioxide layer, and the manufacturing method of the graphite silver paste layer is different from that of the embodiment 1 in that: step 1) and step 4) are not carried out, and a conventional structure is obtained, namely a manganese dioxide cathode layer, a water-based graphite layer, an oily graphite layer and a silver paste layer are sequentially formed on the surface of the tantalum block;
the dipping process requires that the tantalum blocks are all immersed in the corresponding solution; the ESR of the resulting semi-finished product was measured at a frequency of 100KHz, the shear force being the shear force between the silver paste layer and the graphite layer, and the average value of the data obtained is shown in table 1:
table 1 test results
Fig. 2 is a SEM image of the surface morphology of the manganese dioxide/water-based graphite mixed layer in this example, which can be seen from the following figure: in the embodiment, the surface of the layer is smoother, the defect of uneven surface of the manganese dioxide layer is overcome, the layer is well compounded with the manganese dioxide layer, contains micropores, can play a role in adsorbing water-based graphite, and further enhances the binding force.
Example 2
A method for reducing ESR of a solid electrolyte tantalum capacitor graphite silver paste procedure is to prepare a graphite silver paste layer on the surface of a tantalum core with a dielectric oxide film and a manganese dioxide layer, wherein the graphite silver paste layer is prepared by the following steps:
1) Immersing tantalum block in the mixed solution A, immediately taking out the tantalum block, dehydrating the tantalum block at 35deg.C for 15min, and decomposing in a capsule furnace at 230deg.C with oxygen content of 4% for 8min, mostCooling at room temperature for 5min to obtain a first layer of cathode (i.e. a mixed layer of manganese dioxide and water-based graphite); the mixed solution A is prepared from an aqueous graphite solution with a solid content of 15wt% and a concentration of 2.05g/cm 3 Is prepared by mixing manganese nitrate solution according to the volume ratio of 5:1;
2) Immersing the tantalum block treated in the step 1) in an aqueous graphite solution with the solid content of 15wt%, immediately taking out the tantalum block, dehydrating the tantalum block for 35min at 18 ℃, solidifying the tantalum block for 30min at 190 ℃, and finally cooling the tantalum block for 5min at room temperature to obtain a second-layer cathode (namely an aqueous graphite layer);
3) Immersing the tantalum block treated in the step 2) into oily graphite with the solid content of 30wt%, immediately taking out the tantalum block, dehydrating the tantalum block at 25 ℃ for 40min, solidifying the tantalum block at 170 ℃ for 30min, and finally cooling the tantalum block at room temperature for 5min to obtain a third-layer cathode (namely an oily graphite layer);
4) Immersing the tantalum block treated in the step 3) in the mixed solution B, immediately taking out the tantalum block, dehydrating the tantalum block at 25 ℃ for 30min, solidifying the tantalum block at 190 ℃ for 30min, then heating to 220 ℃ for 30min, and finally cooling the tantalum block at room temperature for 8min to obtain a fourth layer of cathode (namely an oily graphite and silver paste mixed layer); the mixed solution A is formed by mixing an oily graphite solution with the solid content of 30wt% and silver paste with the solid content of 50wt% according to the volume ratio of 2:1;
5) Immersing the tantalum block treated in the step 4) into silver paste with the solid content of 50wt%, immediately taking out the tantalum block, dehydrating the tantalum block for 30min at 20 ℃, solidifying the tantalum block for 30min at 220 ℃, and finally cooling the tantalum block for 5min at room temperature to obtain a fifth-layer cathode (namely a silver paste layer);
comparative example 2
A method for reducing ESR of a solid electrolyte tantalum capacitor graphite silver paste procedure is to prepare a graphite silver paste layer on the surface of a tantalum core with a dielectric oxide film and a manganese dioxide layer, and the manufacturing method of the graphite silver paste layer is different from that of the embodiment 2 in that: step 1) and step 4) are not carried out, and a conventional structure is obtained, namely a manganese dioxide cathode layer, a water-based graphite layer, an oily graphite layer and a silver paste layer are sequentially formed on the surface of the tantalum block;
the dipping process requires that the tantalum blocks are all immersed in the corresponding solution; the ESR of the resulting semi-finished product was measured at a frequency of 100KHz, the shear force being the shear force between the silver paste layer and the graphite layer, and the average value of the data obtained is shown in table 2:
table 2 test results
Example 3
A method for reducing ESR of a solid electrolyte tantalum capacitor graphite silver paste procedure is to prepare a graphite silver paste layer on the surface of a tantalum core with a dielectric oxide film and a manganese dioxide layer, wherein the graphite silver paste layer is prepared by the following steps:
1) Immersing the tantalum block in the mixed solution A, immediately taking out the tantalum block, dehydrating the tantalum block at 15 ℃ for 45min, then placing the tantalum block in a film furnace with the temperature of 260 ℃ and the oxygen content of 4.5% for decomposition for 10min, and finally cooling the tantalum block at room temperature for 8min to obtain a first layer of cathode (namely a manganese dioxide and water-based graphite mixed layer); the mixed solution A is prepared from an aqueous graphite solution with a solid content of 1wt% and a concentration of 2g/cm 3 Is prepared by mixing manganese nitrate solution according to the volume ratio of 1:1;
2) Immersing the tantalum block treated in the step 1) in an aqueous graphite solution with the solid content of 5wt%, immediately taking out the tantalum block, dehydrating the tantalum block for 35min at 20 ℃, solidifying the tantalum block for 30min at 160 ℃, and finally cooling the tantalum block for 7min at room temperature to obtain a second-layer cathode (namely an aqueous graphite layer);
3) Immersing the tantalum block treated in the step 2) into oily graphite with the solid content of 20wt%, immediately taking out the tantalum block, dehydrating the tantalum block at 25 ℃ for 40min, solidifying the tantalum block at 175 ℃ for 30min, and finally cooling the tantalum block at room temperature for 5min to obtain a third-layer cathode (namely an oily graphite layer);
4) Immersing the tantalum block treated in the step 3) in the mixed solution B, immediately taking out the tantalum block, dehydrating the tantalum block at 25 ℃ for 30min, solidifying the tantalum block at 160 ℃ for 30min, then heating to 200 ℃ for 30min, and finally cooling the tantalum block at room temperature for 8min to obtain a fourth layer of cathode (namely an oily graphite and silver paste mixed layer); the mixed solution A is formed by mixing an oily graphite solution with the solid content of 20wt% and silver paste with the solid content of 45wt% according to the volume ratio of 4:1;
5) Immersing the tantalum block treated in the step 4) into silver paste with the solid content of 35wt%, immediately taking out the tantalum block, dehydrating the tantalum block for 30min at 20 ℃, solidifying the tantalum block for 30min at 200 ℃, and finally cooling the tantalum block for 5min at room temperature to obtain a fifth-layer cathode (namely a silver paste layer);
comparative example 3
A method for reducing ESR of a solid electrolyte tantalum capacitor graphite silver paste procedure is to prepare a graphite silver paste layer on the surface of a tantalum core with a dielectric oxide film and a manganese dioxide layer, and the manufacturing method of the graphite silver paste layer is different from that of the embodiment 3 in that: step 1) and step 4) are not carried out, and a conventional structure is obtained, namely a manganese dioxide cathode layer, a water-based graphite layer, an oily graphite layer and a silver paste layer are sequentially formed on the surface of the tantalum block;
the dipping process requires that the tantalum blocks are all immersed in the corresponding solution; the ESR of the resulting semi-finished product was measured at a frequency of 100KHz, the shear force being the shear force between the silver paste layer and the graphite layer, and the average value of the data obtained is shown in table 3:
table 3 test results
From the above results, it can be seen that: the conventional structure is that a manganese dioxide cathode layer (coarse), a water-based graphite layer (smooth), an oil-based graphite layer and a silver paste layer are sequentially formed on the surface of a tantalum block; however, the surface of manganese dioxide is rugged and has a large number of holes, and since the silver paste contains an organic binder, the viscosity is high and the paste is directly coated on the surface of manganese dioxide, the contact resistance is increased, and the loss characteristics of the tantalum capacitor are damaged. The use of graphite can thus improve the electrical contact between the silver layer and the manganese dioxide layer. Namely, the water-based graphite has a connecting effect, the oil-based graphite has a higher solid content, has an ESR reducing effect and a certain stress resisting effect, and the silver paste layer has a capacity leading-out effect of the capacitor; however, the application considers that the uneven surface of the manganese dioxide is difficult to be directly filled by the aqueous graphite layer, so that a mixed layer of the manganese dioxide cathode layer and the aqueous graphite layer is added between the manganese dioxide cathode layer and the aqueous graphite layer, thereby playing a role in transition and buffering and improving the binding force.
Meanwhile, in the conventional structure, the silver paste layer is composed of a polymer matrix, silver powder, chemical additives, other adhesives and the like, has hydrophobicity, and the oily graphite layer has hydrophilicity, so that a phenomenon similar to water-in-oil phenomenon is caused, a certain contact angle exists between the graphite layer and the silver paste layer, and the graphite layer and the silver paste layer are not completely mutually dissolved, so that a series of problems such as stripping of the layer, poor contact tightness and the like occur after the silver paste layer is dried at a high temperature, and as a result, the electric parameters of a sample are deteriorated, and the ESR value is increased. The oily graphite and silver paste mixed layer is added between the oily graphite layer and the silver paste layer, the oily graphite and silver paste mixed layer has hydrophilicity and hydrophobicity, and is similar to the function of double faced adhesive tape, so that tight connection is formed between the silver paste layer and the graphite layer, an interactive three-dimensional network structure is formed between the layers, and the contact resistance (ESR) is reduced.
Claims (10)
1. A method for reducing ESR of a graphite silver paste process of a solid electrolyte sheet type tantalum capacitor is characterized in that a graphite silver paste layer is prepared on the surface of a tantalum core with a dielectric oxide film and a manganese dioxide layer, and the graphite silver paste layer is prepared by the following method:
1) Immersing tantalum blocks in a mixed solution of an aqueous graphite solution and a manganese nitrate solution, and then dehydrating, decomposing and cooling to obtain a first layer of cathode;
2) Immersing the tantalum block in a water-based graphite solution, and then dehydrating, solidifying and cooling to obtain a second-layer cathode;
3) Immersing the tantalum block in an oily graphite solution, and then dehydrating, solidifying and cooling to obtain a third-layer cathode;
4) Immersing tantalum blocks in a mixed solution of an oily graphite solution and silver paste, and then dehydrating, solidifying and cooling to obtain a fourth-layer cathode;
5) Immersing the tantalum block in silver paste, dehydrating, solidifying and cooling to obtain the fifth-layer cathode.
2. The method for reducing ESR of graphite silver paste process of solid electrolyte sheet type tantalum capacitor according to claim 1, wherein said manganese nitrate solution has a concentration of 0.75-2.05 g/cm 3 。
3. The method for reducing ESR in the graphite silver paste process of a solid electrolyte sheet type tantalum capacitor according to claim 1, wherein the aqueous graphite solution is prepared by mixing aqueous graphite with deionized water, and the solid content after mixing is 0.5-15 wt%.
4. The method for reducing ESR of graphite paste process of solid electrolyte sheet type tantalum capacitor according to claim 1, wherein in step 1), the volume ratio of aqueous graphite solution to manganese nitrate solution in said mixed solution is (1-8): 1.
5. The method for reducing ESR in the graphite silver paste process of a solid electrolyte sheet type tantalum capacitor according to claim 1, wherein the oily graphite solution is prepared by mixing oily graphite with deionized water, and the solid content after mixing is 15-30wt%.
6. The method for reducing ESR in the graphite silver paste process of a solid electrolyte sheet type tantalum capacitor of claim 1, wherein said silver paste has a solid content of 25 to 50wt%.
7. The method for reducing ESR in the graphite silver paste process of a solid electrolyte sheet type tantalum capacitor according to claim 1, wherein in said step 4), the volume ratio of said oily graphite solution to silver paste in said mixed solution is (2-4): 1.
8. The method for reducing ESR in the graphite silver paste process of a solid electrolyte sheet type tantalum capacitor according to claim 1, wherein the dehydration time is 5 to 85min and the dehydration temperature is 10 to 100 ℃.
9. The method for reducing ESR in the graphite silver paste process of the solid electrolyte sheet type tantalum capacitor of claim 1, wherein the decomposition time is 5-20 min and the decomposition temperature is 150-300 ℃.
10. The method for reducing the ESR of the graphite silver paste process of the solid electrolyte sheet type tantalum capacitor according to claim 1, wherein the curing time is 5-60 min, and the curing temperature is 120-350 ℃; the cooling time is 5-30 min.
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